💥 Two planets collide under astronomers' watch

What happens when two planets collide? Astronomers have just observed the aftermath in real time around a distant star.

The star Gaia20ehk, similar to our Sun, suddenly began to flicker starting in 2016. Located about 11,000 light-years away, it exhibited dips in brightness followed by chaotic variations, unexpected behavior for a star of this type. Researchers immediately suspected that an extraordinary phenomenon had just occurred in its immediate vicinity.


By analyzing the data, the team led by Anastasios Tzanidakis discovered that the brightness fluctuations were caused by clouds of dust and rock passing in front of the star. These debris likely came from an impact between two planetary bodies in orbit. Astronomers used several telescopes to confirm this hypothesis, thus capturing the trace of a rare event in real time.

To better understand, scientists observed Gaia20ehk in infrared light. They found that when the visible light decreased, the infrared light increased sharply. This signature indicates that the matter blocking the star was very hot, superheated. According to the researchers, these observations correspond to the consequence of two colliding planets.

This collision is reminiscent of the one that formed our Moon approximately 4.5 billion years ago. The debris orbits at a distance similar to that between Earth and the Sun, which could lead to the formation of an exomoon around a new planet. We are therefore dealing with a case reproducing the past of our own planet, in orbit around a similar star, and at a similar distance.

The frequency of these impacts is of major interest for astrobiology. The Moon played a key role in the development of life on Earth, by influencing tides and tectonics. Observing other collisions could reveal whether habitable worlds are common in the galaxy. Astronomers now hope to detect more similar events to refine their models.

Planet formation through collisions

Planets are born from small pieces of matter called planetesimals, which orbit young stars. Early in the life of a stellar system, these bodies frequently collide, merging to create larger worlds. This chaotic process lasts for hundreds of millions of years before the system stabilizes, giving rise to planets like those in our Solar System.

These impacts are normal during the formation phase, but they become rare once the system reaches equilibrium. Collisions can differ in intensity, ranging from gentle encounters to catastrophic shocks that vaporize part of the materials. In the case of Gaia20ehk, the observed event seems to be large-scale, producing enough debris to obscure the star.

Observing such events from a distance is difficult because they require perfect alignment between the star, the planets, and Earth. Furthermore, the light signals are unpredictable, requiring continuous monitoring. Technological advances and the accumulation of data now make it possible to detect these phenomena more easily.

This knowledge helps scientists reconstruct the history of our own world. By understanding how collisions shape planets, we can better predict the diversity of exoplanets and their properties, such as the presence of moons or atmospheres.

The role of the Moon in Earth's habitability

Our Moon is not just a simple satellite; it profoundly influences life on Earth. By stabilizing our planet's axis of rotation, it maintains a relatively constant climate over long periods. Without this stability, conditions could change extremely, making the development of biology more difficult.

Ocean tides, caused by the Moon's gravitational pull, mix waters and promote chemical exchanges on a global scale. This continuous movement contributes to the circulation of nutrients and the evolution of marine ecosystems. Furthermore, some theories propose that the Moon could play a role in tectonic activity, by exerting forces that aid plate movement.

The Moon also offers partial protection against asteroid impacts. This shielding effect reduces the risk of massive collisions that could wipe out life. Thus, the presence of a large natural satellite seems to be an important factor in creating a hospitable environment.

The frequency of collisions like that of Gaia20ehk, and their ability to produce moons, allows us to estimate how many worlds in the galaxy could be habitable. If such events are common, it increases the chances of finding planets with moons similar to ours, and perhaps life elsewhere.